1. Field of the Invention
The present invention relates to an exhaust device of an engine in a vehicle such as a motorcycle.
2. Description of the Related Art
An exhaust device of an engine in a vehicle for racing used particularly in a motocross race or the like for example is structurally designed to have reduced weight and suppress decrease in output performance. That is, a main pipe having punching holes is provided through a muffler body, and glass wool as a sound absorbing material is stuffed in the space between the muffler body and the main pipe. A cylindrical member formed by rolling a metallic wire cloth and steel wool is inserted between the main pipe and the glass wool.
Incidentally, noise regulations on engine exhaust sound in this type of vehicle are tightened year after year. Then, reduction in exhaust sound becomes necessary, and as a measure thereof, for example, a structure is employed in which a resistive element such as a punching cone is attached to a front portion in the main pipe or a tail pipe part, so as to lead the energy of sound efficiently to the glass wool.    Patent Document 1: Japanese Patent No. 3445875
However, there is a problem in the above-described structure that the glass wool is displaced forward or backward by receiving the pressure of exhaust gas, where the sound absorbing effect decreases and the exhaust sound increases, or a heat problem occurs such that the temperature of the muffler body increases by the influence of exhaust heat. Moreover, when it is attempted to address the displacement by the glass wool itself, there are a method to use molded wool, a method to wrap with glass wool in a mat form, and the like, but they have a problem of cost increase.
Note that in Patent Document 1, a support member is provided to inhibit movement of the glass wool as a sound absorbing material attached in the muffler.